This invention relates to burnishers for cabinet scrapers for forming "hook" cutting edges on such scrapers.
Hand woodworking cutting tools have blades of two principal types, both of which have cutting edges formed by the intersection of blade surfaces at an acute angle. Generally, blades that make what is called a shearing cut have cutting edge geometry in which the imaginary plane bisecting the acute angle formed by the cutting edge tool surfaces lies entirely in or near the body of the blade. Examples of such tools include chisels, smoothing plane blades, lathe skews and gouges, and pocket knives. Other tools generally referred to as "scrapers" have a cutting edge in the form of a "hook", and the imaginary plane bisecting the angle formed by the tool surfaces at the cutting edge lies generally perpendicular to the plane within which the body of the blade lies. The principal examples of such tools are cabinet scrapers, scraping plane blades, and bowl scraper lathe turning tools.
Important among these scraping tools are cabinet scrapers, which are deceptively simple in appearance but very useful for removing extremely fine layers of wood or finish, while leaving a very smooth, level surface. The most commonly used cabinet scraper configuration is a flat rectangular sheet of spring steel on the order of 1/32nd inch thick and roughly the size of a small index card. Alternative shapes of cabinet scrapers have curved, rather than straight edges, and typically available thicknesses range between 0.015" (0.4 mm) and 0.042" (1.0 mm).
Such cabinet scrapers are prepared for use by grinding or filing and honing the edge so that it is straight (or smoothly curved in the case of curved scrapers), very smooth, and square to the scraper body. A "hook" may then be formed along the scraper edge by drawing the burnisher along the edge while it is oriented at an angle varying between approximately 90.degree. and 75.degree. to an imaginary line normal to the scraper edge and lying within the plane of the scraper plate. Typical burnishers are smooth, hardened steel rods having oval, round, rectangular, square or triangular cross sections and a handle. While burnishers intended solely for use with cabinet scrapers are widely available, the backs of woodworking chisels are also usable, as are other suitably shaped rods provided, in each case, that the hardness of the burnisher is greater than that of the cabinet scraper.
The typical technique for forming a hook on a cabinet scraper with a burnisher involves mounting the cabinet scraper in a vise and drawing the burnisher across the scraper's edge while holding both ends of the burnisher with it oriented during sequential passes at angles decreasing from approximately 90.degree. to no less than approximately 75.degree..
The principal drawback associated with this hook-forming method is the difficulty of accurately and reproducibly selecting and maintaining the angle at which the burnisher is oriented. This problem is most acutely experienced by neophytes.
A wheel burnisher is also available for forming the hook with a hardened steel wheel, but the angle of contact between the burnishing wheel in such devices and the scraper edge cannot be varied.
There is, accordingly, a need for a burnishing apparatus sufficiently simple to be competitive in cost with conventional burnishers but able to maintain a selected relative angular position between the burnisher and scraper blade.